Pitot pumps are a form of centrifugal pump. Typically, a pitot pump is constructed by providing a hollow rotatable casing disposed within a surrounding housing. A plurality of radial tubes in the walls of the casing force the fluid to be pumped outwardly through the ducts by centrifugal force as the casing is rotated, the fluid being discharged into the casing. A stationary pitot tube in the interior of the casing intercepts the rotating fluid in the casing, the ram effect forcing fluid out through the pitot tube. Pitot pumps of this type are well known, as shown in U.S. Pat. Nos. 3,795,459, 3,817,659, and 3,838,939, all of which are owned by the assignee of the present invention.
It has furthermore been proposed heretofore to use pitot pumps to pump oil produced from a well, which oil may contain contaminants such as notably sand, which it is desirable to remove from the oil being pumped. Pitot pumps can be used to provide both pumping action for the oil and as a centrifugal separator by which sand or other contaminants are removed from the oil as the oil is pressurized. Whether utilized as a pump or a pump-separator, the pump includes a stationary vane projecting inside the casing which is used to support the pitot tube and which also operates to agitate the centrifically separated accumulations of contaminant matter on the casing inner surface at the outer periphery of the chamber in the casing. This vane should be made as thin as possible in a direction parallel to the axis of rotation of the casing in order to minimize interference with the rotating mass of fluid within the interior of the casing. However, in the past the fluid pumped into the housing of the casing through the radial ducts through centrifugal force had a large component velocity of flow in a direction parallel to the axis of rotation, thus imposing a substantial lateral force on the stationary vane (a force in the direction parallel to the axis of rotation), imposing a severe strain on the relatively thin vane. This lateral force is not constant but pulsates as each discharge duct rotates past the region of the vane. This pulsating force has in some cases resulted in structural failure of the stationary vane.